Hole Trapping of G-Quartets in a G-Quadruplex

摘要

Since reduction and oxidation of DNA are essential processes occurring in various biological phenomena, electron and hole transfer in DNA has drawn recent attention because of its importance and potential application in biological science and nano-biotechnology, respectively. In practice, it is known that the reduction of DNA closely relates to the repair of damaged DNA such as a T-T cyclobutane lesion, whereas the oxidation of DNA promotes oxidative damage, apoptosis, and cancer. Thus, it is important to understand the mechanisms and dynamics of DNA-mediated charge-transfer processes. Excess electron transfer (EET) in DNA has been studied by various techniques, such as laser flash photolysis, γ-ray radiolysis,'4' or product analysis which were used to analyze the cleavage of 5-bromo-2'-deoxyuridine (BrdU) or the T-T dimer in DNA by photoinduced electron transfer. The laser flash photolysis is conducted principally on short-length DNA, which is containing four A-T base pairs between two chromophores. Meanwhile, the DNA-mediated hole transfer occurs over a distance greater than 20 nm and the migration of the hole along the DNA involves many steps of short-distance charge-transfer processes between stacked guanine (G) bases because guanine among the four natural DNA bases is most sensitive to oxidation. The hole transfer rate depends on the inserted nucleobase between the G-C base pairs. In addition, the derealization of the charge over the stacked G bases along the DNA stem has also been reported.